Unraveling Flooding Dynamics and Nutrients’ Controls upon Phytoplankton Functional Dynamics in Amazonian Floodplain Lakes

Cleber Kraus,Marie-Paule Bonnet,Ludgero Cardoso Galli Vieira,Jérémie Garnier,Maria Morais Pereira Souza Lobo,David Da Motta Marques,Ina De Souza Nogueira

doi:10.3390/w11010154

Abstract

The processes in tropical floodplain lakes enable maintaining phytoplankton nutrient requirements over a hydrological year. The nutrients such as nitrogen, phosphorus and carbon compounds play an essential role in phytoplankton growth. However, the way that nutrients and phytoplankton interact and how this relationship varies seasonally in tropical freshwater ecosystems is not clear. In this study, we evaluate the relationship between phytoplankton–nutrients over the hydrological cycle in Amazonian floodplain lakes and verify if this relationship influences the biomass of cyanobacteria. We also check what factors linked to nutrients act in structuring phytoplankton community. Using the phytoplankton functional approach, we verified how their ability to respond to hydrological and environmental variations reflects the ecological conditions and investigated how these interactions work. The results show that the Amazonian floodplain lakes could maintain long-term nutrient enrichment status. The nutrients input conduces to cyanobacteria dominance, that allied to other factors, play an essential role in supporting the stability of the phytoplankton–nutrients relationship over the hydrological cycle.

Highlights

Nutrients are factors that may limiting the primary productivity of the phytoplankton community [1,2,3], and affect the efficiency in food chain ecological transfers [4]
The partial redundancy analysis for partition environmental data shows that both, nutrients and hydrological variables, had a significant influence in structuring the phytoplankton community, but the strength of the nutrients partition was higher than that of hydrological variables (Table 2)
The analyses show that only the hydrological variation is strong enough to produce functional changes in the phytoplankton community and this reflects the importance of flood pulse dynamics in the Amazon basin

Summary

Introduction

Nutrients are factors that may limiting the primary productivity of the phytoplankton community [1,2,3], and affect the efficiency in food chain ecological transfers [4]. Due to its low concentration in relatively pristine freshwater environments [5], phosphorus (P) in its bioavailable form for autotrophic organisms (orthophosphate) has long been considered as the main limiting factor for primary production [6]. Disentangling what nutrient (P or N) is the most significant for primary production is strongly dependent on the environmental conditions and biological characteristics (especially related to phytoplankton community) prevailing in the considered aquatic ecosystem [6,7,11,12]

Objectives

Methods

Results

Discussion

Conclusion